I have a 95 GT vert. I recently installed a new Kenwood in dash receiver. I put in the 5 volt converter so no popping like the unit that came out. I have noticed, the top rear speakers do not work. The subs below do and the fronts all work. I used wiring harness adapters so those should be good. If I move the audio to the front everything still works, including the factory subs by the rear seats. If I shift audio to the rear no sound at all. Could this be a blown amp in the Mach system or crossover in the system. I really don't know much about how the system is laid out to start troubleshooting.

I'm not sure what the converter does but, if you have an amplified stock system (obviously you do) most of the time you cannot run an aftermarket deck because you are running line power to the amp. I'm assuming the converter you have is between the deck and the stock amp? If so I would check, check, and recheck all my connections.

For the speakers there really was no connections to be made. Wiring harness plugged into stereo and then in to factory plug. the only connections were the power and grounds and such. The Mach is a weird system, hence looking for some input from those that know it well.

Score one for Crutchfield. I pulled the stereo and started chasing continuity. Turns out the solder joints in the adapter from the RCA amp pre-outs to the factory harness were bad. Called crutchfield and they are sending me a new adapter for free. Im glad it was just a ****ty adapter not not a blown crossover